How do I begin to teach Ken how to swim? The option never arised for me
You have to start Ken Samantha Sharing Route first. Then when you go to their house and you find them having sex, there will be a dialogue of you inviting Ken to come to the Beach as well but turns out he can't swim and you have to offer to teach him.
On the same day, go to the Public Pool and rent it for $3,000. Do this 3 times to get all the Pool scenes with Ken and Samantha. Also there is a bonus scene with Adrian, Ken and Samantha in the Public Pool as well.
There are 3 photos that you have to show Ken to trigger the Ken Samantha Sharing Route if you want to see the whole dialogues from him.
1st Photo: any photo at the Beach
2nd Photo: the third photo in Ken's House ( Samantha shows her ass )
3rd Photo: while you and Samantha having sex
After knowing that you and Samantha having sex with each other, Ken will ask for your help to convince Samantha. Talk to Samantha in her Bedroom and tell her that Ken is a virgin and he's not happy. Talk to Ken again and tell him to just join in the next time you're having sex with Samantha ( Tuesday / Friday )